1. Field of the Invention
The present invention relates to a single-chip color imaging apparatus and method.
2. Description of the Related Art
In the conventional single-chip color imaging apparatus using a CCD (charge-coupled device) or the like as a solid-state image sensor, filters for three primary colors R (red), G (green) and B (blue), respectively, are disposed in a positions corresponding to pixels of the CCD. In this color imaging apparatus, a luminance signal is produced based on a light incident upon the CCD, and color signals are produced correspondingly to the light incident upon the CCD through the three primary color filters. Namely, R, G and B color signals are produced correspondingly to a light incident upon the CCD pixels on which the three primary color filters are disposed.
In the CCD used in the color imaging apparatus, R, G and B color filters are provided for pixels, respectively, and disposed horizontally in a sequence of R, G, R, G, . . . , R and G, for example. Color signals are produced correspondingly to the three primary color filters on the pixels. Therefore, in such a CCD, a G color signal will not be produced from a pixel on which an R color filter is provided and it should be produced by interpolation of color signals.
That is, for a horizontal interpolation of color signals from pixels to acquire an interpolated image, color signals from pixels disposed successively in the horizontal direction are added together and averaged. Similarly, for a vertical interpolation, color signals from pixels disposed successively in the vertical direction are added together and averaged. For acquisition of a G color signal from a CCD pixel on which the R color filter is disposed, the above-mentioned interpolation is effected. For produce a pixel data through an interpolation, values indicative of vertical and horizontal correlations are detected. For this detection, signals from pixels surrounding the pixel in consideration are filtered for calculation. Further in this color imaging apparatus, interpolated pixel data acquired by interpolation are weighted by the correlation values.
However, since the photosensors for pixels in the CCD are different in sensitivity from each other, there will exist a difference in amplitude between a G signal from a G pixel included in a horizontal line of R, G, R, G, . . . , R and G color filters and a G signal from a G pixel included in a horizontal line of G, B, G, B, . . . , G and B color filters. Therefore, in a single-chip color imaging apparatus, when a luminance signal is produced from color signals from pixels in each horizontal line, the above difference in sensitivity from one photosensor to the other will cause a difference in amplitude between luminance signals from the pixels in different horizontal lines and it will appear as a horizontal stripe-like noise in a monitoring image and captured image.